Antiarrhythmic drugs play a major role in the management of the most common types of arrhythmias. The margin between the beneficial and toxic effects of these drugs is often narrow. Thus, a precise knowledge of dosages, drug-target tissue interactions, pharmacodynamics and pharmacokinetics of antiarrhythmic drugs is needed to better predict how effective a particular drug will be in the treatment of a specific arrhythmia in a given patient. Despite the large amount of information that is available on the electrophysiological and pharmacological effects of antiarrhythmic drugs, we still do not know enough about their true mechanism of action in individual patients. The results of the Cardiac Arrhythmia Suppression Trial (CAST) firmly established that the use of class I drugs is potentially dangerous in a specific subset of patients. Additionally, several meta-analyses have reported that quinidine has severe proarrhythmic effects in patients with atrial fibrillation. The management of arrhythmias in elderly patients is difficult because of age-related factors that may influence the pharmacokinetics and pharmacodynamics of antiarrhythmic drugs.